1Department of Anthropology, Indiana University, Bloomington, 2Department of Radiology, University of Pennsylvania
Friday 9:30-9:45, Galleria North
Fossil endocranial surfaces provide the most direct evidence of brain evolution, yet they reflect only a fraction of the actual variation in brain anatomy. Ultimately, the goal is to make assessments of the behavioral implications of variation in endocranial form. Broca’s cap appears to be larger on the surface of the left endocranial hemisphere in hominins, which is suggestive of elaboration in brain function relevant to language. While brain size has been shown to be significantly associated with both group size and vocalization repertoire size in primates, direct studies of endocranial morphology and behavior has not been attempted. We used non-rigid deformation techniques to quantify localized variation in endocranial morphology across 13 primate specimens using CT scans from the Open Research Scan Archive. Behavioral data for group size and vocalization repertoire size were extracted from the literature. Correlations were calculated between behavioral variables and the degree of localized distortion required to morph each species’ endocranial form into a common atlas (Pan troglodytes). Maps of the endocranial surface illustrating these correlations on a voxel-by-voxel basis suggest that vocal repertoire size is associated with variation in Broca’s cap, superior and dorsal lateral prefrontal, orbital frontal and anterior cerebellar areas. Group size correlations were less obvious and localized in orbital frontal and the anterior temporal regions. These results suggest vocal repertoire size and group size may leave signals on the endocranial surface; furthermore, suggestive associations around Broca’s cap may have implications for the relationship between non-human primate vocal behavior and language.
This study was supported by funding from the National Science Foundation (NSF-0447271) and Indiana University.